1. Field of the Invention
The present invention relates to a method for the production of a protein concentrate useful in the manufacture of margarine of the type which has a low calorie value and a high content of proteins. More particularly the invention relates to a method for the production of a protein concentrate from skimmed milk for subsequent use in the manufacture of so-called low calorie margarine of water-in-oil type having a fat content of 35-60 percent.
2. Description of the Prior Art
A method for the production of low calorie margarine of the water-in-oil type is previously known in which a water phase is emulsified in a fat phase and in which the water phase is produced from a protein concentrate from buttermilk emanating from a butter and/or butteroil manufacturing process. Such a protein concentrate from buttermilk has good water keeping properties and emulsifying properties and is well suited for the production of low calorie margarine. The supply of buttermilk, however, is relatively restricted whereas the supply of skimmed milk is relatively good. Consequently, it has been desirable to produce a low calorie margarine of water-in-oil type having a high protein content, in which the protein concentrate for said low calorie margarine is obtained from skimmed milk.
A method for the production of low calorie margarine is also previously known in which the water phase is produced with skimmed milk as the starting material and in which the protein comprises milk casein obtained by precipitation with an acid. In this method a water-in-oil emulsion is obtained by dispersing up to 60% water phase in down to 40% fat phase in a closed cooling and crystallization system at a temperature at which the fat begins to crystallize. Before the water phase is dispersed in the fat phase the protein containing water phase is heated to a temperature of between 65.degree. and 80.degree. C. and is kept at said temperature for a period of between 10 and 30 minutes.
This previously known method involves some disadvantages, which are mainly based on the difficulty of obtaining a stable emulsion having as high content of water phase as, for example, up to 60% and the difficulty of obtaining a product having a microbiological keepability. In the known method it is considered necessary to keep the pH-value at a relatively low level and less than 6, and a pasteurization must be made at a high temperature for a long period of time in order to obtain a product which is sufficiently stable and substantially free of microbiological changes. The precipitation of the proteins from the starting material in this method is a time consuming operation and acids must be added. Also in order to make emulsification of the water phase in the fat phase possible the fat phase must be cooled before mixing the two phases together. Furthermore, in the production of the water phase mineral acids and organic acids are added which necessarily influence the composition of the protein concentrate. The added chemicals thereafter must be washed out by an expensive and complicated process before the protein concentrate is mixed into the fat phase. As a result a large amount of the valuable so called "whey proteins" are lost since they cannot be precipitated by an ordinary acidification.
Also previously known is a method for the production of a low calorie margarine having a protein concentrate from skimmed milk wherein the milk raw material is first acidified to pH 5.1-5.8, and is thereafter subjected to a membrane filtering, and the resulting protein concentrate is then subjected to a special thermic treatment. By virtue of the membrane filtering a relatively large amount of the whey proteins is obtained which proteins cannot be precipitated by acidification. The whey proteins obtained in this matter change the character of the protein concentrate to give improved water-keeping and emulsifying properties. It is necessary in the membrane process, however, that particular apparatus be available which can be relatively expensive.
Protein concentrate for low calorie margarine of water-in-oil type having a high protein content also can be manufactured from different caseins, but problems appear in such manufacture, for example, bad taste such as a glue taste.
Another possible protein raw material might be quark. It is however, difficult to provide the desired product with sufficiently high dry substance content and protein content using quark as the protein material. Normal quark also is a product which is difficult to handle and which causes difficulties in separation, pumping and cooling. These difficulties are especially accentuated at such long operation periods which are necessary in the manufacture of low calorie margarines on an industrial scale.
Furthermore, quark contains a large number of added bacteria and other bacteria which unfavourably influence the bacteriological quality of the final product and when storing a final product prepared using quark it develops proteinases. This is especially obvious after a free storing and following thawing both of the protein concentrate (the quark) and the ready product (the low calorie margarine). In addition, quark contains rennet enzyme. The bacteria and other enzymes may give poor taste like a cheese taste.